Roof structure designed and fabricated

The roof structure for a commercial office development where the individual timber trusses weighed close to a tonne each has been designed and made by a member of the TRA.

A member of the Trussed Rafter Association (TRA) has designed and fabricated the roof structure for a commercial office development where, in order to accommodate the length of span and the imposed loads, the individual timber trusses weighed close to a tonne each.

The contract, carried out by Harlow Timber Systems, was for Westleigh Developments and concerned the construction of a three-storey office block in Lutterworth.

With an over-plate dimension of 17.6 metres to address, the most economic solution was to fabricate sets of three trusses in the conventional fashion for each position, then screw them together as a single assembly in the factory.

While the main frame to the building was of structural steel, the project structural engineers worked together with the architects and wanted to avoid having more girders spanning the building at second floor ceiling level.

The use of the timber trussed rafters was therefore decided on as the most economic solution.

In addition to the main trusses weighing 895 kilograms each, Harlow Timber Systems also supplied a variety of other fabrications to form the hipped end to the roof and to accommodate a lift shaft.

The latter involved designing a set of mono-pitch trusses to fit one side of the lift shaft, which was just off centre to the building, with stub versions on the opposite, shorter side.

The TRA member's package was completed with the provision of all the cut timbers and ancillary brackets necessary to complete the roof structure.

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